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[1 Svo] Flemming's knock theory - question (fwd)
> Flemming wrote:
> stay right on the hairy edge - without breaking anything. There is still
> some power to be made with a detonating engine - look at anything
> running a nitrogen-based fuel like NOS or nitromethane - both serious
> octane degreders. But how long do they last? [Answer to rhetorical
> question:] Some do, some don't.
I didn't think NOS was a "fuel"...just an oxidizer...
> Later EEC strategy narowed the window where it will listen for
> detonation - I wrote an article on that already if you want to search
> the SVOOA back issues. Anyway detonation can only occur between 5 and 20
> degrees ATDC so there's no reason to listen during the remaining 700
> degrees of rotation for that cylnder. In a 4-cylinder engine, that comes
> to 680 degrees of "don;t care" rotation. The 84/85 strategies
> (recognized by the early manifold design) weren't selective enough and
> the "hammer" test would retard timing easily.
Something you wrote didn't make sense...you mentioned that detonation can
occur in a 15 degree window per cylinder on the power stroke right? So 4
cylinders X 15 degrees a piece is a total of 60 degrees. Out of 720
degrees of crank rotation, you have 660 degrees of what you call "Don't
care" rotation. My question is, how does the computer know precisely what
position the crank is in? For that matter, how can the computer possible
know what cylinder is on it's power stroke? It can't...In my experience
the EEC-IV in the 2.3 Turbos use the vane in the distributor simply for a
reference point for spark dwell and injector firing. Because of this
system, it is impossible for the computer to know what the exact position
of the crank is...it only knows that the vane representing _some_ cylinder
just went by the PIP, so now it can wait a specified time unit based on
other engine info before it collapses the field of the coil and causes a
spark at the NEXT cylinder in the firing order. This is how the computer
can "advance" the timing from the base, but NOT retard it past the base.
So how can the software get smarter when it comes to listening for knocks
if it has to "guess" where it's at? I am not an expert, but I would see it
much easier and more effective from a design standpoint to relocate the
knock sensor, or listen for a different frequency. My guess would be
that's why Ford played with the location of the knock sensor on the
2.3's...do you have any proof that this "knock algorithm" exists? This is
by no means a flame...I am very curious how Ford implemented this "scheme"
of listening for knocks.
> Now, from a testing viewpoint, did you reconnect the KS and notice the
> same documentable decrease in performance?
In my experience, again, my '88 TC stuff is very sensitive about
connecting the knock sensor. If I connect it, I slow down enough to "feel"
it...this is with 92 octane, stock timing, stock ignition, and 15-16